20 THE ANNELIDA POLYCHAETA. 



e. Body anteriorly either wholly without a group of filiform or branched branchial appendages/ 

 or these if present arising from the frayed margin of a campanuliform membrane sur- 

 rounding the mouth except ventrally. 

 /. With branched or arborescent branchiae on middle region of the body. . . . Arenicolidae. 

 ff. With no branchiae on middle region of body. 



g. No capillary setae, both notopodia and neuropodia bearing exclusively crochets, 

 crochets few, with tori not elongate; body long, somites numerous; prostomium 



without appendages Uncinasetidae. 



gg. Capillary setae present. Tori much elongated with crochets numerous. 



h. The first three fascicles of notopodial setae without corresponding ventral setae; 

 uncinigerous tori elongate and very narrow, almost line-like; branchiae often 



present as the frayed margin of a circumoral membrane Ammocharidae. 



hh. Either some other number than first three pairs of fascicles of notopodial setae or 

 none at all without corresponding ventral setae; uncinigerous tori not line-hke, 

 usually elliptic or oblong; never with a group of branchiae about the mouth. 



Maldanidae. 



ee. Body anteriorly with a group of filiform, dendritic or plumose branchiae. . . . Terebelloidea. 



f. With two pairs of tentacular cirri; the most posterior division of the body consisting of 



five or six somites abruptly offset from the rest of the body, this caudal region short, 



flat and commonly ending in a short, thread-like process or cirrus Amphictenidae. 



ff. With no tentacular cirri ; most posterior division of body not of this form, consisting of 



more than ten somites. 



g. Prostomium more or less fused with the peristomium and forming a supraoral lobe 



which bears numerous filiform tentacles, often in two groups, which are not at all 



retractile within the oesophagus; branchiae never more than three pairs, these 



commonly branched, or if simple nearly always of uniform thickness, filiform, only 



rarely subulate; anterior region never bearing series of stout paleae. . Terebellidae. 



gg. Prostomium distinct; tentacles retractile within the oesophagus; branchiae most 



commonly four pairs, rarely only three or two pairs, always simple and strongly 



pointed or subulate; third somite often bearing two rows of conspicuous paleae. 



Ampharetidae. 

 dd. Crochets either lacking entirely on the first nine or more somites or, if present, never in 

 unmixed groups or series but mingled with capillary setae. 



e. Buccal armature complex, including several to many pairs of maxillae Leodicoidea. 



f. No ventral cirri present; dorsal cirri rudimentary or foliaceous Lumbrinereidae. 



ff. Dorsal and ventral cirri present. 



g. Maxillae consisting of a few pieces only, these forming short series. 



h. A pair of frontal tentacles, and a total of seven; peristomium entire. . Onuphididae. 

 hh. No frontal tentacles, the total from one to five; peristomium biannulate. 



Leodicidae. 



gg. Maxillae numerous, small, forming two long series Dorvilleidae. 



ee. Buccal armature simple or none. 



/. Capillary setae present only on the first nine to fourteen somites; elsewhere only crochets 

 in series at the ends of which are the branchiae when present; tentacles two, small 

 and retractile; parapodia in anterior region rudimentary, in the posterior none. 



Capitellidae. 

 ff. Setae not thus arranged. 



g. Body on each side above the parapodia with a series of nearly globular capsules (cirri) 

 each of which contains a tube wound in a ball; parapodia uniramous and without 



acicula Sphaerodoridae. 



gg. Without such capsular cirri and non-aciculiferous parapodia. 



h. Prostomium long, conical and strongly annulated; bearing four short tentacles 



at its tip Glyceroidea. 



i. Parapodia of one form throughout the length of the body; proboscis with four 



similar jaws Glyceridae. 



ii. Anterior parapodia uniramous, the others biramous; proboscis with numerous 



pieces in its armature Goniadidae. 



hh. Prostomium not thus annulated and with four tentacles at its tip. 



i. Prostomium without true tentacles; palpi absent or else present in the form of 

 two greatly elongated tentaculiform bodies. 



